Electric circuit interrupter



Feb. 24, 1948. w. E. PAUL 2,436,665

ELECTRIC G IRCUIT INTERRUPTER Filed Deo. 27, 1944 I5 Sheets-Sheet 1 bhs/Attorney Feb 24, 1948 v w. E. PAUL 2,436,665

ELECTRIC `CIRCUIT INTERRUPTER Filed Dec. 27,` 1944 s sheets-sheet 2 Inventor: William E. Paul,

by imm/M Feb. 24, 1948. w. E. PAUL ELECTRIC CIRCUIT INTERRUPTER Filed Dec. 27, 1944 3 Sheets-Sheet .3

Inventor. William E Paul, by v/i//yw His Attfmey.

Patented Feb. 24, 1948 2.436.665 ELECTRIC CIRCUIT INTERRUPTER William E. Paul,.Schenectady, N. Y., assigner to General Electric Company,

New York a corporation of Application December 27, 1944, Serial No. 569,943 17 Claims. '(Cl. 20o-148) My invention relates to electric circuit interrupters, and more particularly to an arc extinguishing structure for electric circuit interrupters which will more eiilcielitly interrupt the circuit than larrangements used heretofore. Specifically my invention is an improvement on my prior Patents 1,805,497 and Reissue 18,257, granted May 19 and November 24, 1931, respectively, and assigned to the same assignee as the present application.

Circuit interrupting devices generally in use today employ what might be termed the brute force method of interrupting the circuit. By that is meant that the interrupting contacts are separated indiscriminately so that the arc is permitted to form as it will and then extinguishment thereof is attempted. It is obvious-that if in an alternating current circuit the contacts were separated at substantially the zero point of the current wave, little or no arcing would result. For manyyears attempts have been made to design electric circuit breakers embodying this principle. However, circuit interrupters have only recently begun to be -sufficiently consistent in their operation to make the matter of selecting the zero in the current wave important. Furthermore, most of the arrangements for selecting the zero point in the current wave have required such complicated apparatus as to be impractical.

It is an yobject of my invention to provide a new and improved zero current selector for an electric circuit breaker.

It is another object of my invention to provide an electric circuit breaker which interrupts the current with' little or no arcing, winch is simple and compact in construction, inexpensive to manufacture and very eiilcient in operation.

It is another object of my invention to provide a new and improved air blast circuit breaker which interrupts the circuit at substantially the zero point ofthe current wave of the alternating current circuit to be interrupted.

Still another object of my invention is to provide a new and .improved fluid blast circuit interrupter with mens for conserving the fiuld so that more eilicient operation is obtained.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawings in which Fig. 1 is a View, partly in section, of a circuit lnterrupter embodying my invention; Fig. 2 is a sectional View taken on line 2 2 of Fig. 1, assuming that Fig. 1 shows a complete structure; Fig. 3 is a sectional view taken on line 3-3 of Fig. 1 assuming that Fig. 1 shows a complete structure; Figs. 4, 5 and 6 are schematic diagrams illustrating successive positions of certain parts of the device embodying my invention during the circuit interrupting operation; Fig. 7 is a perspective view of a number of elements of the circuit interrupter embodying my invention; Fig. 8 is a perspective view partly in section of a portion of the circuit interrupter of Fig. l, and Fig. 9 is a schematic diagram of a circuit interrupting device illustrating a modification of my invention.

Although it will become apparent as the following description proceeds that my invention is applicable to various types of electric circuit breakers, I have chosen to specifically illustrate my invention in connection with a fluid blast circuit breaker preferably an air blast circuit breaker. Although my invention is also adapted for use with single4 or polyphase circuit breakers. for the sake of simplifying the drawings I have chosen to illustrate my invention in 'connection with a single phase circuit breaker.

Referring now to the drawings, there is illustrated an electric circuit breaker including an arc extinguishing structure or chamber generally indicated at I within which is mounted a ilrst or main pair of relatively movable contacts comprising a stationary contact generally indicated at 2, and a movable blade-type contact generally indicated at 3. Relatively movable contacts 2 and 3 are essentially current carrying contacts, the contact 2 comprising a plurality of spring biased contact fingers 4 and longer ngers 5. Movable contact 3 is provided with an extension 6 adapted to cooperate with fingers 5, the circuit breaker in the drawings being shown in the partially open position just after the fingers 5 and extension 6 have sep rated. Any suitable means (not shown) for proucing relative movement of contacts 2 and 3 may be provided. Preferably, movable contact 3 is connected to a suitable iiuid motor or the like in a manner disclosed and claimed in copending application Serial No. 562,296, Boisseau and Bold, filed November 7, 1944, and assigned to the same assignee as the present application.

The arc extinguishing structure I is a boxlike structure formed of insulating material comprising side plates I and 8, end plates 9 and I9 and plate il. In order to insure no leakage of air and to increase the electrical creepage path, the plates 'L S, 9, l0 and il, as best shown in Figs. 1, 3A andv 8, are tongued and grooved and iitted together. so as to form a unitary structure held together by bolts l2. Essentially arc extinguishing structure l is divided into two chambers i3 and lll, respectively, separated by an insulating partition l5, suitably interrelated with side plates 'l and 8, as is clearly shown in Fig. 8. Communication between chambers l3 and M can occur only through a rectangular Aopening i6 in partition l5, which opening is positioned substantially interbinediate the ends of partition l5. Partition i is held in place by suitable bolts il extending through the side plates i and 8 of the arc extinguishing structure l. -Stationary contact 2 is suitably supported in chamber i3 and is engageable by movable contact 3 which extends through an opening iB in end plate lil.

In order to supply a blast of fluid under pressure in arc extinguishing chamber i, I have provided a source of iiuid generally indicated at I@ which is connected-through a blast valve schematically indicated at 2U and a conduit 2| with an opening 22 in plate il intermediate the ends of plate il and substantially opposite the opening i8 in partition l5. A suitable plate 23, bolts 2Q, and a gasket (not shown) insure a sealed relationship between the air conduit 2l and the opening 22 in plate il.

Movable contact 3 is electrically connected to a sliding contact 25 including a plurality of contact fingers 26 biased into contacting engagement by spring means 2l. The contact ngers 26 are best shown in Fig. 8 while the spring means are best shown in Fig. 1. When the-movable contact 3 is pulled out of opening i8 and consequently free of sliding contact 25, the fingers 26 engage with eachother and effectively provide a gate vso that iluid under pressure such as air, is prevented from escaping from chamber i3 except through open'- ing i8.

It will be obvious vto those skilled in the art that it is difcult to operate a main large blast y valve such as 2U with sufilcient precision and speed both in opening and closing so that a large quantity of air is not lost unnecessarily during a circuit breaker operation. In order to effect a substantial conservation of this otherwise lost air, I provide-an auxiliary air valvethat cooperates` directly with the contacts and which permits a blast of air to iiow only when ythe cony tacts have reached the point of separation and which stops the blast just as soon as it is no longer needed. The main blast valve 2li may be operated in the usual manner. This auxiliary valve is illustrated in the drawings as a slide valve 28 comprising a rectangular plate of insulating material having an opening 29 therein. Slide valve 28 is permitted a limited reciprocal vertical travel between relatively movable contacts 2 -and 3 and partition l5. Preferably slide valve 28 op crates peumatically, butA its travel is controlled by movement of the adjacent blade-type contact d and to this end blade-type contact 3 is illustrated as provided with an extension 3D whose upper end abuttingly engages the slide valve 2d. vIn order to withstand the end pressure of blade extension 30 the insulating material of slide valve 23 is reinforced by a metal insert Si positioned so as to engage the extension t@ on blade 3, as best shown in Figs. l and 8.

The end plate lil is provided with vent opening 32 adjacent the opening i8 so that blast pressure within chamber i3 is effective to move slide valve 28 downward during the opening,

ing on the upper end of slide valve 28 adjacent stationary contact 2 biases the valve to its down position since the lower end of slide valve 28 is freely vented to atmosphere by virtue of the opening 32 in end plate lll. When no blast of fluid is present in chamber I3, 4element 30 integrally formed with contact 3 will Serve to move slide 'valve 2t toward its closed position during closing movement of contact 3 against the force of gravity acting on slide valve 28. The remaining volume within chamber i3 that is not occupied by stationary contacts 2 or blade contact 3 is completely filled with blocks of insulating material such as 32B and 315, best shown in Fig. 2. With this arrangement. a minimum of air is required since no unnecessary air spaces are present which must belled before the blast of iiuid becomes effective.

The stationary contact 2 is preferably connected to a line terminal in any suitable manner. In Fig. 1 this line terminal is schematically illustrated at 35. Similarly, the movable contact 3 may be connected toa line terminal 36 through a sliding contact ora ilexible lead.

The arrangement described thus far is not capable per se of interrupting high currents and in accordance with my invention I provide in chamber lil the zero selector device of my invention which interrupts the current with little or no arcing. This zero selector device comprises a pair of Zero selector units 3l and 38 provided with hinge pins 39 and lill, respectively, so as to be pivotally mounted to the side `walls l and 8 of the arc extinguishing structure i, these side walls Each of the zero selectingl units 3l and 38 is substantially identical and accordingly only one of these units BI will be described in detail while the correspcnding'parts of the other unit are designated by the same reference numerals. As is best shown in Figs. 1 and 3, Zero selecting unit 3l comprises a plurality of insulating members di, (i2, d3 and dlt, each having portions thereof cut away so that when these members are itted together as is shown in Fig. 3, they will provide a hollow space for accommodating a force coil d5. This force coil d5 comprises a strip of conducting material such as copper, as is best shown in Fig. 3, wound in the form of a coil, as is best shown in Fig. 1, with a layer of insulating material i6 also in strip form separating the adjacent layers of the coil 45. This coil is wound about a deflectable resilient core member Jil. Preferably, deflecting member il is formed sion members, also formed of which will become more apparent' as the following description proceeds.

In order to make deecting member 41 still lighter a plurality of holes 49, best shown in Figs. 1 and 3, are drilled longitudinally thereof. One end of deflecting member 41 is adapted to be ilxedly supportedin zero selecting unit 31 and to this end is provided with a pair of laterally extending ears 58, clearly shown in Fig. '1. The ilxed end of deflecting member 41 is provided with a slot5l into which one end 52 of coil 45 may be inserted and electrically connected thereto, as by welding or the like. The deflecting end of defiecting member 41-.is provided with an open- \ing\53 into Whichis inserted an arcing contact 54 which cooperates with asimilar arcing contact 5.5 associated with zero selecting unit 38.

Arcing contact 54 is suitably supported as by screws 56 from the free or iiecting member 41 and arcing tip of arc resistant 61. The zero selecting units 31 and 38 including the coils 46 are provided with openings 58 through which arcing contacts 54 and 55 may extend so that arcing tips 51 may be engagement. Furthermore each of these zero selecting units 31 and 38 is provided with a cutaway portion 59.

The other end of force coil 45 indicated at 68 in Fig. 1 is preferably inserted in aslot in pin39 and suitably welded or otherwise fastened thereto in good current carrying relationship. It will be observed that the set of contacts comprising arcing contacts 54 and 55 is connected across hinge pins 39 and 40 and may be traced through the force coils 45, deflecting members 41 and arcing contacts 54 and 55.

In accordance with my invention the circuit through arcing contacts 54 and 55 is connected across line terminals `35 and 36 in parallel with relatively movable current carrying contacts 2 and 3. Accordingly, hinge pin 39 is illustrated as being connected with stationary contact 2 through a terminal 6|, exible conductors 62 and is provided with an a conductor bar 63. Similarly, hinge pin 48 is` connected with sliding contact 25 through a terminal 64, flexible conductors 65 and conducting bar 66. It will be understood that side plate 1 will be provided with recesses for accommodating these conducting members which recesses are of sufllcient size tov permit limited pivotal movement of terminals 6l and 64.

In order to prevent the force coils 45 from spreading due to the magnetic forces involved, the zero selecting units 31 and 38 are reinforced by a plurality of nonmagnetic tension members 61 which extend across coils 46 and are held in position by suitable bolts 68. These tension members may be formed lfrom any n-onmagnetic material, such as brass or the like. Adjacent the fixed end of deilectins member 41 there is provided a pair of special tension members 68 and 18 best shown in Figs. 1 and 7. These tenfrom nonrnagnetic material, are provided with cooperating vnotches ears 50 of deflecting member 47 therebyv xedly deflecting end of dematerial, indicated at in electrical circuit through the second for accommodating the lateral extensions or indicatedin Figs. 1, 4 and 8 arcing contacts 54 and 55 are in current carrying engagement. Normally the zero selecting units 31 and 38 are biased to the closed position indicated in Figs. 1 and 4I by means of suitable springs 12 and 13, respectively. Spring 12 is inserted through an opening 14 in end platel 9 so that one end thereof engages zero selecting unit 31. Similarly, spring 13 is inserted through an opening 15 in end plate I8 with one end thereof engaging zero selecting unit 38. The other end of spring 12 engages with a pivotally mounted member 16 having .a latching arm 11 and a tripping arm 18. Pivotally mounted member 16 is hingedly supported ,to a member 19 suitably supported from end plate 9 as by bolts 80. The latching arm 1.1 of pivotally mounted member 16 extends into an opening 8i in zero selecting unit 31 so that the notch 82 thereof engages the end of deecting member" whereby deilecting member 41 is normally held in the current carrying position indicated in Figs. l and 4. The tripping extension 18 has a portion thereof extending into chamber I4 so as to be engaged by zero selecting unit 31 upon pivotal movement in a counterclockwise direction thereof. Such counterclockwise direction of zero selecting unit 31 will engage the tripping extension 18 of pivotally gagement with a desirable to provide suitable cooling means which anchoring this end of deflecting member 41 in.

each zero selector unit 31 and. 38.

The zero selecting units 31 and 38 are mounted, respectively, above and below the blast opening I6 in partition l5, and substantiallyll the chamber I4 as is best shownin zero selective units 31 and 38 are in the positions Fig. 8.' Whenv have been indicated mounted member 16 to cause counter-clockwise rotationl thereof with the resultant release of the latchingl member 11 relative to defiecting member 41.

..Similarly, the other end of rspring 13 is in enpivotally mounted member 83 which also includes a latching extension 84 and a tripping extension 85 identical with extensions 11 and 18 described above. Member 83 is pivotally mounted to member 86 supported from end plate I8 as by bolts 81. Latching extension 84 extends into an opening 88 in zero selecting unit 38 so that the notch 89 thereof normally engages the end of defiecting member 41 associated with zero selecting units 38. It will be obvious from the above description that spring means v12 and 13 normally bias both the associated zero selecting units` 31 and 38, respectively, and the associated latching extensions 11 and 84, respectively, into the positions indicated in Figs. l and 4.

An arc cutting cross barrier 98 is provided in chamber 4 and is supported from side plates 1 and 8 as by bolt SI on the center line between zero selecting units 31 and 38. The middle portion of this arc cross barrier 98 is reduced to a V- section whose knife edge lies closely adjacent to the arcing tips 51 for dividing the extinguishing blast as is best shown in Figs. 1 and 4. The extended side portions of this arc cross barrier 90 fits snugly into corresponding cut-away portions 59 of zero selecting units 31 and 38 whereby fluid under pressure entering chamber i4 through opening I6 is substantially conned in its flow to impinge arc cross barrier 80 to the convergentdivergent passage between zero selecting units 31'and 38 and side walls 1 and 8 as is most clearly illustrated by Fig. 6.

In `order to cool the arc gases ilowing above and below the are cross barrier 88, it may be at 92 and 93. As is best shown in Fig. 3 the are cooling means 93 comprises a plurality of spaced metal plates 94 suitably held together as a unit byA bolts 95.

AFrom the above description it is obvious that the current is normally carried by main contacts 2 and 3. Upon relative separation ci' confer of current through tacts 2 and 3 the current can be carried through the parallel circuit including arcing contacts 54 and 55. In order to be sure-that this transfer of current is readily made it is desirable to introduce a reactance drop in the circuit o! the main contacts 2 and 3. This is accomplished by surrouding the movable blade 3 with a ring of iron or other magnetic material. As isbest'shown in Figs. 1 and 2, insulating plate II is provided with an insert 96 of iron or other magnetic material, while insulating blocks 33 and 34 adjacent movable contact 3 are provided with inserts 31 and 98, respectively, also of magnetic material. The insert 3| in slide valve 25 described above, preferably is provided with an enlarged portion 3 I best shown in Fig. 8, to'complete the magnetic. ring around blade. contact 3. Ii desired the lowerv portion of insert 3I may be.formed of nonmagnetic material, such as brass, so that the magnetic ring around blade contact 3 is initially incomplete and therefore produces substantially no reactance. At about the time that the transarcing contacts. and 55 is desired the magnetic portion 3|' has moved to the position indicated in Figs. 1 and 2 to complete the magnetic ring, thereby introducing the desired reactance for causing rready transfer of the current from the main contacts 2 and 3 to the arcing contacts 54 and 55.

With the circuit breaker in the closed position the arcing contacts and 5 are in current carrying engagement and in view of the impedance of force coils 45 substantially all'the current flows through main contacts 2 and 3. To initiate an opening operation of the circuit breaker movable contact 3 is actuated and blast valve 20 is operated. High pressure air is admitted into the chamber I3 in the conventional manner. When movable contact 3 reaches a position so that arcing tips 5 and 6 begin to separate, the current is shunted to the parallel circuit already deiined through the zero selecting units 31 and 3B with the current flowing through the force coils 45 and the deecting members 41. It will be obvious from the drawings that a sulllciently high current flowing in force coils 45 will produce a magnetic leld which reacts with the magnetic iield produced by the current flowing in deflecting members 41 thereby forcing the deiiecting members 41 in a direction to hold arcing contacts 54 and 55 in'curre'nt carrying engagement. The magnetic ringfcomprising members 3|', 98, 81 and 98, around movable contact 3 ,causes 'the current to be transferred to arcing contacts 54 and 55 witl'rrio arcing. As Ythe main current carrying contacts separate slide valve 2B moves downwardly so that at the point of separation opening 29 coincides to a limited lextent with opening. I6 whereby a blast of air under pressure scours the main current carrying contacts 2 and 3 and enters chamber I4'. As already explained, the highpressure above slide valve 25` 8 lector units 31 and 38, respectively. The deflected position of deecting members 41 is shown in Fig. 5.. When the zero selecting units 31 and 33 strike the tripping projections or extensions 1l and 85, respectively, the latching extensions 11 and 34 are moved out of latching engagement with deflecting members 41. This suddenly releases defiecting'members 41 and the inherent stillness thereof tends to cause them to assume their non-deilected position. If at the instant that latching extensions 11 are released the instantaneous current flowing in force coils 45 is high, members 41 will still remain deected due to the electro-magnetic force exerted upon them by the-force lcoils 45 sothat arcing contacts 54 and 55 remain in current carrying engagement.

` This condition is clearly indicated. by the schematic arrangement shown in Fig. 5,. As the instantaneous current becomes smaller and smaller along the decline of the alternating current wave,

a' point is reached just ahead of the current zero of the current wave where the forces due to the stillness of deecting members 41 exceed the "magnetic forces tending to keep them deiected and in the position indicated in Fig. 5, where- 41 snapback to normal 'position thus separating arcing contacts 54 and 55, as is clearly shown in Fig, 6.' The very insignificant arc formed between arcing contacts 54 and 55, by virtue of the tact that they did not separate precisely at the zero point of the current wave, is blasted against the sharpedge of arc splitter 90 and extinguished in the well known manner, the arc gases finally exiting through arc coolers 92 and 33.

Following the interruption of the current flow,

slide valve 28 has moved down to its maximum forces the valve downward so that it closely fol lows movable contact 3 with stop-strip or exy'A tension 30 secured tothe contact 3 in abutting engagement with the slide valve insert 3|;

When the fluid or air under pressure is ad- .mitted to chamber I4 it immediately causes zero travel position thereby again closing the opening I5 precisely in accordance with contact travel to prevent the loss of unnecessary air until the main blast valve 23 subsequently closes the air supply to arc extinguishing structure I. The blade 3 is then drawn clear of the arc extinguishing structure I with the ngers 25 of sliding contact 25 acting as gates to prevent the loss of air through the blade opening I8 until the main blast valve 20 is closed. Upon cessation of the blast, the pressure in chamber I4 subsides so that the zero selecting units 31 and 38 return to their biased closed latched positions, as shown in Fig. l. The slidevalve 28 remains in its lower closed position until a subsequent breaker closing operation. v'

The closing of the breaker is' eiiected by contacts 2 and 3 by virtue of the fact that the slide valve 23 is in such a position if a blast of iluid under/pressure is supplied during the cios'- ing strokel to permit this fluid under pressure to openarcing contacts 54 and 55. These arcing ,contacts are closed after the air blast'is shut on. From the above description it will be obvious that the limiting factor, as far as the interrupting ability of the circuit breaker is concerned. is the mechanical strength of the zero selecting units with respect to the magnetic forces involved. It would be desirable if zero selecting units such as 31 and 38 couldbe designed for application to all sizes of circuit breakers regardless of the current to be interrupted, in which event the zero selecting units would be identical for lall circuit breakers. If the zero selecting units were designed to withstand magnetic -iorces produced by currents oi the magnitude of say 40.000 amperes and below. any magnitude of current above this value may be interrupted in accordance with the modification of my invention illustrated in Fig. y9. The corresponding parts of Fig. 9 are designated by the same reference numerals as in the preceding figures. The selector units 31 and 38 are identical with the selector units described above. It is assumed by way of example, that the selector units 31 and 38 are designed to satisfactorily withstand the magnetic forces involved with currents up to and including 40,000 amperes. In accordance with my invention disclosed in Fig. 9, I provide an auxiliary zero selecting unit 99 in the form of a loop of resilient current conducting material in between conductor 63 and zero selecting unit 31. Similarly, an auxiliary zero selecting unit I is connected between conductor 66 and zero selecting unit 38. Zero selecting units 99 and |00 are designed so that with current exceeding 40,000 amperes flowing therethrough they close associated contacts IOI and |02, re-

spectively. Contacts |0I and |02 are interconnected by an impedance generally indicated at |03 which is substantially the same as the impedance of the circuit through zero selectors 31 and 38. If a current of 80,000 amperes is shunted through conductors 63 and 68 upon opening of main current carrying contacts 2 and 3, contacts and |02 will be closed and the 80,000 amperes will divide so that 40,000 amperes flow through impedance |03 and 40,000 amperes flow through selector units 31 and 38. As soon as the instantaneous alternating current decreases below 40,000 amperes contacts |0| and |02 open automatically and zero selector units 31 and 38 will then function to interrupt the circuit at substantially the zero point with little or no arcing. The proportion of the current carried by impedance I 03 and zero selecting units 31 and 38 is determined by their relative impedances and may be arranged according to the maximum interrupting capacity required. It should be understood that additional auxiliary zero selecting units may be provided for shunting still higher proportions of the total current flowing in the circuit so that the zero selecting interrupting units 31 and 38 are never permitted to carry current in excess of their predetermined current rating.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departp ing from my invention in its broader aspects and I, therefore, aim in the appended claims to cover all such changes and modiilcations as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is: y 1. In a fluid blast circuit breaker, an arc extinguishing chamber, a pair of relatively movable contacts associated with said chamber, a

source of iluid under pressure, means including a blast valve interconnecting said source and said chamber, and an auxiliary slide valve formed of insulating material and having a surface against which fluid supplied to said chamber when said blast valve is open exerts a force to cause said slide valve to press against one of said contacts,

said slide valve being operable in response to movement of said one contact for preventing a blast of fluid from extinguishing said are even though said blast valve is opened, until a predeterminer! movement of said one contact has occurred.

2. In va iluid blast circuit breaker, an arc extinguishing chamber, a pair of relatively movable contacts associated with said chamber, a source of fluid under pressure, means including a blast valve interconnecting said source and said chamber, means defining a large opening into said chamber and an auxiliary slide valve containing an aperture therein said opening and aperture being out of registry during the closed position of said breaker so that no fluid under pressure may be supplied to said chamber even though said blast valve is opened, and means including said fluid under pressure for causing said slide valve to move in response to movement of one of said contactsto supply a blast of fluid to saidVV chamber by registry of said opening with said aperture upon a predetermined movement of said one contact.

3. In an electric circuit interruptor for alternating current circuits comprising a pair of main current carrying contacts, a pair of auxiliary contactsfmeans for transferring the current from said current carrying contacts to said auxiliary contacts during a circuit interrupting operation, a pair of pivotally mounted zero selector units one associated with each of said auxiliary contacts, each of said zero selector units comprising a defiecting member supporting its associated auxiliary contact and a force producing winding connected in series with said associated auxiliary contact and closely associated with said deflecting member, means for latching said auxiliary contacts in the closed position, means for causing pivotal rndvement of said zero selector units, and means responsive to pivotal movement of said zero selector units for releasing said latching means, said force coils causing said associated deiiecting members to deflect and hold said auxiliary contacts in engagement until a predetermined low value of instantaneous current is attained, the resilience of said deflecting members causing high speed separation of said auxiliary contacts at substantially current zero.

4. In an electric circuit interrupter i'or alternating current circuits comprising a pair of main current carrying contacts, a pair of auxiliary contacts, means for transferring the current from said current carrying contacts to said auxiliary contacts during a circuit interrupting operation, a movably mounted zero selector unit associated with one of said auxiliary contacts comprising a deflecting member supporting said one auxiliary contact and a force producing winding connected in series with said one contact, means for latching said auxiliary contacts in the closed position, means for causing movement of said zero selector unit, and means responsive to movement of said zero selector unit for releasing said latching meanssaid force coil causing said deflecting member to deflect and hold said auxiliary contacts in engagement until a predetermined low instfgitaneous current value approachcontacts during a circuit interrupting operation,

a pivotally mounted zero selector unit associated with one of said auxiliary contacts comprising a deilecting member supporting said one auxiliary contact and a force producing winding connected in series with said one auxiliary contact, means for latching said auxiliary contacts in the closed position, means for causing pivotal movement of said zero selector unit, and means responsive to pivotal movement of saidr zero selector unit for releasing said latching means, said force coil causing said deflecting member to dev selector unit associated with one-oi said contacts comprising a deflecting member for supporting said one contact and a force producing winding connected in series with said contact, means for latching said contacts in the closed position,

means for moving said zero selector unit, and

means responsive to movement of said zero selector unit for-releasing said latching means, said force coil causing said defiecting member to deect and hold said contacts in engagement until a predetermined low instantaneous current value is attained.

7. In an electric circuit interrupter for alternating current circuits comprising a pair of relatively movable contacts. a movably mounted zero selector unit associated with one of said contacts comprising a deiiecting member for supporting said one contact and a force vproducing member connected in series with said contact, `meansfor latching said contacts in the closed position, fluid means for moving said zero selector unit, and means responsive to movement of said zero selector unit for releasing said latching means,

- said force producing member causing said deflecting member to deiiect and hold said contacts in engagement until av predetermined low instantaneous current value is attained.

8. In an electric circuit interrupter for alternating current circuits comprising a pair of relatively movable main current carrying contacts, a. pair of relatively movable auxiliary contacts, means for transferring the current from said current carrying contacts to said auxiliary contacts during a circuit interrupting operation com-- prising an incomplete ring of magnetic material surrounding a movable one of said main contacts, and means movable with said one contact for completing said ring of magnetic material. i

9. In an electric circuit interrupter for alternating currentcircuits, a pair of relatively movv able contacts, a zero selector unit associatedl with one of said contacts and normally holding it in a closed position, said zero selector unit comprising a deflecting member Ikfor supporting said one contact, an electro-magnetic means also tending when energized to hold said contacts in the closed position, and means for moving said zero selector unit in a direction to open said contacts, said deflecting member permitting such movement while said electro-magnetic means holds said contacts closed for instantaneous current values therein in excess of a predetermined value..

10. In an electric circuit interrupter for alter- 'nating current circuits, a pair of relatively movable contacts, a zero selector unit associated with one of said contacts vand normally holding it in a closed position, said zero selector unit comprising a deflecting member for supporting said one contact, an electro-magnetic means also l tending when energized to hold said contacts in zero selector unit to deilect said deiiecting member without opening said contacts until a predetermined low value of instantaneous current is attained in said electro-magnetic means.

11. In an electric circuit interrupter for alternating current circuits, a pair of relatively movable contacts, a zero selector unit associated with one of said contacts and normally holding it in a closed position, said zero selector unit comprising a deiiecting member for supporting said one contact, an electro-magnetic means also tending when energized to hold said contacts in the closed position, and fluid means for moving said zero selector unit to deiiect said deiiecting member without opening said contacts until a predetermined low value of instantaneous current is atftained in said electro-magnetic means.

12. In an electric circuit interrupter for alternating current circuits comprising a pair of relatively movable contacts. a: zero selector unit associated with one of said contacts comprising a deecting member for supporting said one contact and a force producing member connected in series with said contact, means for latching said contacts in the closed position, uid means for releasing said latching means, said force producing member causing said deiiecting member to deflect and hold said contacts in engagement until a predetermined low instantaneous value of current is attained.

13. In an'electric circuit interrupter for alternating current circuits comprising a'pair of relatively movable contacts, a zero selector unit associated with one of said contacts comprising a deecting member for supporting said one contact, and an elongated coil having substantially straight sides connected in series with said deflecting member and contact, said coil being so positioned with respect to said deilecting member that the electro-magnetic force produced by the interaction of said coil and said deecting member is such as to tend to hold said one contact in its closed position.

14. In an electric circuit interrupter for alternating current circuits comprising a pair of relatively movable main current carrying contacts, a pair of relativey movable auxiliary contacts, means for transferring the current from said main current carrying contacts to said auxiliary contacts during a circuit interrupting operation comprising an incomplete band of magnetic material lpartially surrounding a movable one of said main contacts when said main current carrying contacts are closed, and means for substantially com..

l5. In an electric circuit interrupter for alternating current circuits. a pair of relatively movable contacts,l a zero selector unit associated with one of said contacts normally holding it in the` closed position, said zero selector unit comprising a'` deecting member for supporting said one contact, an electro-magnetic means also itending whenenergized to hold said one contact in the closed position. means for moving said zero selector unit to deect said defiecting member without openingsaid contacts until a predetermined low value of instantaneous current is attained in said electro-magnetic means. and means responsive to the iiow of a predetermined high value of current through said circuit interrupter for bypassing a predetermined portionI of said current around said zero selector unit.

, 16. In an electric circuit interrupter for alterthe closed position, `'and means for moving said 75 nating current circuits, a pair of relatively movl r. w

13 able contacts. a zero selector unit associated with one of said contacts normally holding it in the closed position, said zero selector unit comprising a deecting member for supportingsaid one contact, an electro-magnetic means also tending when energized to hold said contacts in the closed position, means for moving said zero selector unit.

contacts in the closed pos tion, said zero selector units comprising a deiiecting member for supporting the associated contact,- an electro-magnetic means for each selector unit also tending when energized to hold said contacts in the closed position, means for moving said zero selector -units to deflect said deflecting members without opening said contacts until a predetermined low value of instantaneous current is attained in said electro-magnetic means, a normally open circuit having substantially the impedance of said zero selector units connected in parallel with said units, and means responsive to the ow of a predetermined high value of current through said circuitA interrupter for closing said normally open circuit to bypass a predetermined portion of said current around said zero selector units.

WILLIAM Eiy PAUL.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS Number Name Date 1,805,497 Paul May 19, 1931 1,873,388 Greenwood Aug. 23, 1932 2,108,560 Kesselring Feb. 15, 1938 

